NL8200940A - Sample core drilling unit has outer barrel with drill bit - rotatably contg. inner barrel with core catcher axially movable against spring - Google Patents

Abstract

The core drilling unit (1) comprises an outer core barrel (5), which is secured at the lower end of a drilling string and, at its lower end, carries (4) a core drill head (2,3), and an inner core barrel (17) which is rotatably carried (via 13-16) by a swivel (9;10-12) and, at its lower end, carries (22) a core catcher (23). The lower end (24) of this core catcher extends by a small amount below the level (H) at which the annular downward mud passage (26) around the catcher enters a portion (29) with reduced cross-sectional flow area. The inner core barrel is axially movable relative to the outer barrel against spring force (upward to H against spring 31 and possibly downward to L against spring 32). Used as drilling unit to take core samples (35) in underground formation (33). The arrangement gives clear indication if, e.g. through fracture of the core, this can no longer move upwards in the inner barrel, as the catcher is raised (H) and the mud pressure suddenly drops by the flow constriction (29) being eliminated. Drilling is then stopped and damage to the core and to the inner barrel (if in plastic) prevented.

Description

* - _ Λ Ί VO 3128

Title: Core drilling equipment

The invention relates to kera drilling equipment, provided with a core drill pipe which can be fixed at the bottom of a drill series, which carries a core drill bit at the bottom end and a core tube, which is freely suspended in the core drill tube via a rotating bearing and is fitted with a core catch at the bottom end. the lower end of which is located a short distance below the level where a part of a rinsing passage extending downwards around the core catcher is constricted.

In such a known core drilling equipment, an annular hole is drilled by means of core drilling tools, leaving the rock in the middle of the borehole untouched and filling the core housing as the drill progresses.

The purpose of the core tube is therefore to receive a soil sample, the so-called core, in such a way that the core with tube and all of it can be removed from the auditory tube. Since the hearing tube rotates and the core is stationary, the likewise stationary core housing must be suspended in the tube by means of a rotating alloy. Such a rotary alloy can be formed by a ball bearing having a top ring and a bottom ring, the bottom ring being rotatably connected to the hearing tube, the top ring being attached to the stationary core tube.

The core catcher at the bottom end of the core tube serves to receive the core near its base when pulling up the entire drill string, to break away from the rock and to lift it up with the drill string within the core tube.

During core drilling, rinsing fluid pumped down through the drill string is deflected radially outward above the core and passed between the core tube and core casing and directed around the core catcher into a central opening in the core bit for which purpose between the core catcher and the core bit. core bit a ring channel is kept open. This annular channel, in order to keep the core catcher centered, is relatively narrow, however, because this obstructs the mud passage too much in the circumferentially spaced drilling tool, it extends axially over the length of the tool. Extensive recesses are provided so that only in the lower part of the drilling tool is the wall of the flushing passage uninterrupted. The bottom end of the core trap is approximately at the level of this continuous wall zone.

This known construction has a number of drawbacks.

One of these is that if the core gets stuck in the core housing, for example due to breakage, the core can therefore no longer slide up freely in the core housing, the drilling pressure, which may only be applied to the core drill head, is also applied to the core transferred.

The result of this is that the core is pressed together and / or when core housings made of plastic are used, they are damaged, for instance torn open.

Another drawback of the known construction is that when plastic core housings are used, difficulties may arise during the pulling up of the core. After completion of a core drilling operation, as already explained, the drill string must be lifted with the core included, the core catcher being to ensure that the core is separated from the solid rock at its base. In the known construction, the tensile force is transferred to the core catcher via the core housing. Since plastic kera tubes are connected to the bearing and to the core catcher through, for example, steel threaded sleeves attached to it by gluing, it frequently occurs in practice that the connections between the plastic tubes and the steel end sleeves become loose during drawing.

The object of the invention is to avoid these drawbacks of the known art.

For this purpose, according to the invention, the core housing can be moved axially against a pretension relative to the core drill tube.

For example, if an axially active compression spring is arranged above the suspension bearing, when the core gets stuck in the core housing, the core housing will be pushed upwards within the core drill tube, so that the bottom edge of the core catcher, which edge initially extends at the level of the continuous wall portion of the mud passage in the 8200940-3 drilling tool was located within the region of the circumferentially spaced recesses in the mud passage wall, thereby significantly increasing the local drilling mud passage. This is immediately visible at ground level due to a sudden sharp drop in the flushing pressure. Thus, the jamming of the core in the core housing is immediately signaled and core drilling can be stopped or other appropriate measures can be taken.

If an axially active spring is fitted under the suspension bearing, which is useful when using plastic core tubes, the core catcher will clamp around the base of the core when the drill string is pulled up and may remain behind in relation to the core tube and may come into contact with a stop connected to the drilling tool. Thus, when the drill string 15 is further raised, the tensile force will no longer be transferred via the plastic core tube, but via the much stronger core drill tube to the core catcher. When using a metal core housing, the latter spring has no function and is better to be replaced by a metal army retaining sleeve, because on the one hand a metal core housing can exert sufficient tensile force on the core-20 catcher and on the other hand the high weight thereof during core drilling against the core housing. will collapse spring pressure until unwanted contact of the core catcher with the core drilling tool.

To clarify the invention, an embodiment of the core drilling equipment 25 will be described with reference to the drawing.

In the drawing, which shows the bottom end of a core drilling equipment in an axial sectional view, a core drilling tool is indicated by 1. The tool consists of a core bit or bit 2 at the end of a core bit 3, which is threaded 4 is coupled to a core drill tube 5 (outer core barrel), which is attached at the bottom of a drill string (not shown). A sleeve 6 (cartridge cap), which, together with a nipple 7 (Cartridge plug), which is connected to the sleeve 6 by screw thread 8, is mounted within the core drill tube 5, not shown, for mounting a rotating alloy 9 (swivel).

8200940 -4-

The rotating alloy 9 consists of an upper ring 10 and a lower ring 11 with a series of balls 12. The upper ring 10 is connected via a sleeve 13 (bearing retainer) and screw thread 14 to a pipe piece 15 (inner tube plug), to which screw thread 16 core tube 17 (inner core 5 barrel) is suspended. The pipe section 15 is provided with ports 18 which open into an annular flushing passage 19 between the core drill pipe 5 and the core housing 17. A central flushing passage 20 at the bottom of the pipe section 15 can be closed with a ball 21.

At the bottom of the core housing 17 a core catcher 23 is attached by means of screw thread 22, the bottom edge 24 of which delimits a bevel 25. Between the core catcher 23 and the crown 3 of the drilling tool 1 is the extension 26 of the mud passage 19. This part 26 of the mud passage is narrower than at 19, but is locally widened by means formed in the wall 27 of the passage 26. circumferentially distributed axial recesses 28, which extend from the connection 4 of the crown 3 to the core bit 5, to a short distance from the core bit 2. Thus, the bottom part 29 of the flushing passage 26 has a continuous wall and the bottom edge 24 of the core trap 23 is at the level of this. Wall part 29. A stop 30 is formed on the drilling tool 1 at a distance below the bevel 25 of the core catch 23. In the illustrated embodiment, the rotary alloy 9 is socially resiliently mounted between compression springs 31 /. (With slip ring. 31a) and; enclosed, between the sleeve 6 and the top ring 10 and between the nipple 7. By depressing the springs 25 31 or 32, the core tube 17 can move axially with respect to the core drill tube 5, so that the bottom edge 24 of the core catch 23 from the normal level N can be moved to the level H within the region of the recesses 28 and to the level L, where the bevel 25 rests on the stop 30.

The operation of the core drilling equipment is as follows. During normal core drilling, an annular hole 34 is drilled through the core bit 1 in the ground 33. In the center thereof, the core 35 remains, enclosed by the core tube 17 and enclosed at its base by the core trap 23. Under normal conditions, the core housing 17 35 gradually slides down over the core 35, depending on the travel 82 0 0 9 4 0 ..............................

-5- of the drilling tool 1 and the bottom edge 24 of the core catch 23 remains near level N. The central flushing passage 20, which is only used when no core 35 needs to be formed, is closed by the ball 21 and drilling mud is passed through the 5 ports 18 into the mud passage 19, from which it reaches the mud passage 26 along the core catcher 23 and the core drill bit 2. The passage 26 is narrow (measured radially about 4 mm), so that the core catcher remains essentially centered within the drill ready. The recesses 28 provide a local widening of the passage 26, however, they terminate at a distance from the drill bit 2 and at the continuous wall portion 29 the drilling mud experiences a high resistance.

If, for example as a result of a core breakage, sliding the core housing 17 over the core is made more difficult, the core housing 17 will remain behind-15 relative to the downward movement of the core drill tube 5, which is made possible by the according to the invention upper compression spring 31, which is compressed under such conditions. Therefore, the bottom edge 24 of the core trap 23 will move from the level N to the level H, resulting in an abrupt increase in the local passage of the flushing passage 26, in other words the local constriction following the bottom end. of the recesses 28 is suddenly lifted. This is detected remotely by a sudden drop in flushing pressure and measures can be taken to prevent damage to the core housing 17.

In order to raise a core 35 to ground level, the drill string and thus also the core drill tube 5 are pulled out of the borehole 34 with the drilling tool 1. For the core 35 to break off at the base, the core catch 23, the construction of which is such that it can only slide down over the core 35 and clamp on it at the start of an upward movement over the core, must have an upwardly directed force. are practiced. In the known drilling equipments this takes place via the sleeve 6, the nipple 7, the lower bearing ring 11, the pipe piece 15 and the core housing 17. With a steel core housing 17 this need not cause any problems. However, in the increasingly used plastic core housings nowadays, damage often occurs, if not at the tube 17 itself, than at its connections with the tube piece 15 and with the core catcher 23.

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However, the compression spring 32 arranged according to the invention between the bottom ring 11 of the alloy 9 and the nipple 7 allows the core housing 17 to move downwards relative to the core drill tube 5. The lower edge 24 of the core catcher 24 then descends from level N 5 to level L and the bevel 25 rests on the stop 30. The pulling force on the core catcher 23 can then be taken over by the core drill tube 5 and the core housing 17 is unloaded. It is clear that when metal core housings 17 are used, the spring 32 is superfluous for the above-described purpose and it can therefore be replaced by a metal bushing (not shown) between the bottom ring 12 and the nipple 7.

In summary, the axial movability of the core housing 17 within the core drill tube 5, according to the invention, provides an enormous improvement of the core drilling technique, with regard to operational reliability, both during drilling and during raising of a core sample 35.

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Claims (4)

1. Core drilling equipment, provided with a (outer) core drill pipe that can be attached to the bottom of a drill series, which carries a core drill chuck at the bottom end and an (inner) core housing, which is freely suspended in the core drill tube via a rotating alloy and is equipped at the bottom end with a core catcher, the lower end of which is located a short distance below the level where a part of a flushing passage extending downwards around the core catcher is constricted, characterized in that the core housing is movable against prestress, axially with respect to the core tube . 2. Core drilling equipment according to claim 1, characterized in that an axially acting compression spring is arranged above the suspension bearing, which can be compressed over such a distance that the bottom edge of the core catcher is above the level of the constriction in the mud passage around the core catcher. is movable. Core drilling equipment according to claim 1 or 2, in particular with a core housing made of plastic * and with a stop for the core catch located below the level of the core catcher, characterized in that an axially acting compression spring is arranged under the suspension bearing, which can be compressed over such a distance that the core-20 catcher can come into contact with the stop. 4. Core drilling equipment, provided with a core drill tube that can be mounted at the bottom of a drill series, which carries the core drill tool at the bottom end, a mud channel extending centrally through the drilling tool with a smaller diameter in the tool than the inner diameter of the core drill tube, while in the drilling tool has been locally widened over part of its length by the circumferentially spaced recesses in the wall of the passage, said recesses extending axially from the connection to the core casing and further provided with a core housing, which extends through an axial ball bearing with a top ring attached to the core casing and a bottom ring connected to the core casing, is suspended in the core casing and at the bottom end is provided with a kerf catcher, the bottom end of which is located below the level of the axial recesses in the wall of the flush passage in the drill 8200940 i '-8 tool, mad Note that the core bearing suspension bearing is mounted axially resiliently in the core casing by mounting a compression spring above the top ring and / or, when using a core housing made of plastic, a compression spring under the lower ring of the suspension bearing. 8200940 ----------------------------